Scientists have long debated whether Alzheimer’s disease starts in separate regions of the brain independently and at different times, or if it begins in one region and then spreads. Data from researchers at Columbia University Medical Center supports the latter model, showing that abnormal tau protein — a key feature observed in the brains of patients with Alzheimer’s disease — propagates along anatomically connected networks, between connected and vulnerable neurons. The study was published earlier this month in the online journal PLoS ONE [1].